Arranging subscriber billing in telecommunication system

ABSTRACT

The invention relates to a method and a system implementing the method for arranging subscriber billing in a multi-provider environment wherein a subscriber desiring a service uses both a first network (A) and a second network (T). In order to bill the subscriber, either a tariff of the second network (T) is transmitted to the first network (A), a tariff of the first network is combined with the tariff of the second network and the subscriber is billed according to the combined tariff, or a billing identifier is generated in the first network (A) to be transmitted to the second network (T), the billing identifier is attached to billing information in both networks and the pieces of the billing information that comprise the same billing identifier are combined in order to bill the subscriber. The invention thus enables a subscriber in a multi-provider environment to be billed using a single bill.

BACKGROUND OF THE INVENTION

The invention relates to billing a subscriber in a telecommunicationsystem, and particularly to billing a subscriber in a multi-providerenvironment in a mobile communication system. The mobile communicationsystem generally refers to any telecommunication system which enableswireless communication when users move in the service area of thesystem. A typical mobile communication system is a public land mobilenetwork PLMN.

Telecommunication systems are increasingly changing over to amulti-provider environment wherein access is provided by an accessoperator, telephony by a telephony operator and actual services by oneor more service providers. This is the case particularly in systemscalled third generation mobile communication systems, such as auniversal mobile communications system UMTS. In the UMTS, for example,the actual mobile communication network can operate as an access networkproviding the user with wireless access to external networks, such asInternet protocol IP networks and the services thereof, such as IPtelephony IPT. One access network usually provides access to severalexternal networks, which can be of a similar type. There can be severaltelephony operators, for example, which provide the IPT service. Whenthe access operator is not the telephony operator, both operatorstypically collect their billing information in their own networks andbill the subscriber separately. A service provider itself does notmaintain the network but purchases a necessary network service from thenetwork operator, which collects billing information on behalf of theservice provider as if it were the network operator's own billinginformation. The network operator also bills the subscriber on behalf ofthe service provider. In other words, if the service provider purchasesthe network service from the access operator, the access operator isresponsible for collecting the billing information on the service andfor billing according to an agreed tariff. The telephony operatoroperates in a similar manner if the service provider should purchase thenetwork service from the telephony operator.

A service of the mobile communication systems becoming increasinglypopular is a prepaid subscription. The prepaid subscription involves nobilling in arrears but the account of the prepaid subscription ischarged in real time during calls. The prepaid subscription can usuallybe used for chargeable calls until the credits in the subscription'saccount run out, in other words until the prepaid amount has beenexhausted. Usually, the subscriber to the subscription, or someone else,can deposit more money in the subscription's account.

The problem is, however, how to implement a prepaid subscription whichrequires real-time billing during a call in a system comprising anaccess operator and a telephony operator, which both collect their ownbilling information and do not know each other's tariffs. For an enduser, it is inconvenient if he or she is compelled to have at least twoseparate prepaid subscriptions, one being a subscription to the accessoperator and the other to the telephony operator. The same problem alsoarises in connection with a service similar to the prepaid subscriptionwherein the maximum amount of a bill, i.e. the maximum sum of money thata bill is allowed to be during a billing period, has been determined fora subscription to be billed in arrears.

It would also be more convenient for subscribers billed “normally” inarrears to receive a single combined bill instead of separate bills sentby the operators.

BRIEF DESCRIPTION OF THE INVENTION

An object of the invention is thus to provide a method and an apparatusimplementing the method so as to alleviate the above-mentioned problems.

The objects of the invention are achieved by the method andtelecommunication system which are characterized by what is disclosed inthe independent claims. Preferred embodiments of the method and systemof the invention are disclosed in the attached dependent claims.

The idea underlying the invention is that information is transmittedfrom a first network (e.g. a network of a telephony operator or anaccess operator) to a network of a second operator to enable jointbilling. An advantage of the invention is that a subscriber is billed ina centralized manner such that e.g. only a single prepaid subscriptionwill suffice while the operators are still allowed to set their ownprices for their services independently of each other. A furtheradvantage of the invention is that it enables a prepaid subscription ora balance-limited subscription to be paid in arrears to be implementedalso in a multi-provider environment such that the subscriber only needsa single subscription while the operators are still allowed to set theirown prices for their services independently of each other. A stillfurther advantage of the invention is that it is possible to provideboth a user of a prepaid subscription- and a user of a balance-limitedsubscription with the same alternatives to choose a telephony operatorin a multi-provider environment as conventional subscribers (i.e. thoseto be billed normally in arrears).

In a first preferred embodiment of the invention, in a network of atelephony operator, a subscriber is identified as a joint billingsubscriber, i.e. e.g. as a subscriber who has a prepaid subscription toan access network or as a subscriber to be billed in arrears, who wantsto receive, a single bill. When the subscriber has been identified as ajoint billing subscriber, the tariff of the telephony operator istransmitted to the network node of the access operator which isresponsible for billing. The network node combines the telephonyoperator's tariff and the access operator's tariff and charges e.g. theaccount of the prepaid subscription according to the combined tariff. Afurther advantage of the embodiment is that it enables a prepaidsubscription and an account of a balance-limited subscription to be paidin arrears to be charged in real time using an extremely light signalingload.

In a second and a third preferred embodiments of the invention, aglobally unique billing identifier is generated in the network node ofthe access network, and the billing identifier is transmitted to thenetwork nodes which collect billing information, regardless of thenetwork node being a network node of the access network or the telephonyoperator. The identifier enables a billing center responsible forbilling to combine the billing information received from differentoperators. A further advantage of these embodiments is that theyinevitably take into account all special events affecting a billingprocedure.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is now described in closer detail in connection with thepreferred embodiments and with reference to the accompanying drawings,in which

FIG. 1 shows elements of a UMTS system relevant to the invention,

FIG. 2 is a signaling diagram showing a first preferred embodiment ofthe invention,

FIG. 3 is a signaling diagram showing a second preferred embodiment ofthe invention, and

FIG. 4 is a signaling diagram showing a third preferred embodiment ofthe invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention can be applied to any telecommunication systemwherein information necessary for billing a subscriber exists in atleast two different networks. Such systems include systems called thirdgeneration mobile communication systems, such as the universal mobiletelecommunications system UMTS and IS-41, and mobile communicationsystems similar to the GSM system, such as a GSM 1800 and systems basedon the aforementioned systems, such as GSM 2+ systems. The invention canalso be applied to fixed systems wherein two separate operators canoperate. The invention will be described in the following using a 3GPPAII-IP system, i.e. an UMTS system based on IP technology and specifiedin a 3^(rd) generation partnership project 3GPP, as an exemplary system,without restricting the invention thereto. The specifications of mobilecommunication systems, and those of the third generation mobilecommunication systems in particular, are advancing rapidly;consequently, the invention may require additional changes. All wordsand expressions should therefore be interpreted broadly since they areonly intended to illustrate, not to restrict, the invention. Theessential point for the invention is the function, not the network nodein which the function is located.

FIG. 1 shows a simplified network architecture, describing only some ofthe elements of a system architecture. The network nodes illustrated inFIG. 1 are logical units, the implementation of which may differ fromthe described one. It is obvious to one skilled in the art that thesystem may also comprise other functions and structures which need notbe described in closer detail here. In FIG. 1, the broken lines betweennetwork nodes denote signaling connections while the unbroken linesdenote signaling and data transmission links.

In a 3GPP AII-IP system 1, an access layer A and a telephony layer Twill be separated, and both can have operators of their own. The system1 comprises at least one of the both layers. Within the scope of thepresent invention, an access layer corresponds to an access network ofan access operator and a telephony layer corresponds to a telephonenetwork of a telephony operator. Usually, when not roaming, a subscriberalways uses the same access operator while he or she may select thetelephony operator to be used. As far as the invention is concerned, thestructure of the access layer and the telephony layer is irrelevant. The3GPP AII-IP system is based on a GPRS service of the pan-European globalsystem for mobile communications GSM system and an intelligent networkservice implementation according to a customised applications for mobilenetwork enhanced logic CAMEL architecture. The GPRS and the CAMEL areGSM 2+ phase services.

User equipment UE comprises an actual terminal and an identificationcard USIM, also called a subscriber identification unit, detachablyconnected thereto. In this connection, the user equipment UE generallyrefers to a unity comprising the actual terminal and the subscriberidentification unit. The subscriber identification unit USIM is a smartcard which comprises subscriber identity and which performsauthentication algorithms and stores authentication and cipher keys andsubscription information necessary at the user equipment. The actualterminal can be any equipment capable of communicating in a mobilecommunication system. The terminal can thus be a simple terminal forspeech only, or it can be a terminal for various services, operating asa service platform and supporting loading and carrying out differentservice-related functions. The terminal can also be a combination ofseveral different devices, for example a multimedia computer with aNokia card phone connected thereto to provide a mobile connection.

In the first preferred embodiment of the invention according to FIG. 1,the telephony layer T comprises, in addition to the actual IP networkIP, a call state control function CSCF, a media gateway control functionMGCF and an execution environment CSE_T corresponding to a servicecontrol point in an intelligent network.

The CSCF controls call establishment and is responsible for routing, andcomprises, for example, a function corresponding to a switching functionin an intelligent network. The CSCF provides IP telephony services withend-to-end control. Signaling associated with the IP telephony, such asH.323 and SIP, terminates at the user equipment and the CSCF. In otherwords, the CSCF is the network node in which IP telephony user equipmentare registered and via which the signaling is transferred. The CSCFcomprises IP telephony call state models, which are used for controllingcall establishment with other network nodes, such as the service controlpoint CSE_T. The CSCF can also communicate with IP telephony applicationservers (not shown in FIG. 1). The CSCF comprises a subscriber database,which logically corresponds to a visitor location register in the GSMsystem. The CSCF is responsible for producing both telephony billinginformation and service billing information. The telephony billinginformation is used, according to the billing policy and mechanismsspecified by the IP telephony network operator, for billing for the useof basic telephony, different data bearers and additional services. Theservice billing information is generated by the service provider.Service billing is carried out on a pay-by-use basis and calculatedaccording to a contract between the service provider and the subscriber.Both billing procedures are preferably controlled by the service controlfunction in the intelligent network or methods determined by openinterfaces (OSA, Parlay).

In the first preferred embodiment of the invention, the service controlfunction CSE_T of the IP telephony operator controls billing in the IPtelephony network T. In addition, it may control call establishment inan intelligent-network-like manner. The service control function CSE_Tmay comprise all service logic and control associated with billing anddifferent services, and necessary databases or a connection to thedatabases. The service control function is only a logical function andit can be internally implemented in different ways. An alternative isthat it is internally decentralized and the related service logic can bedecentralized in different nodes. Also the service information can bedecentralized in different nodes from the service logic.

The MGCF is an example of new network nodes provided in the network ofthe telephony operator. The MGCF mainly collects information on dataamounts transmitted on the physical connection since the CSCF knowsnothing about them.

In the first preferred embodiment of the invention, the main parts ofthe access layer A are: a core network CN, a UMTS terrestrial radioaccess network UTRAN and a camel service environment CSE_A, whichcorresponds to a service point in an intelligent network.

The UTRAN comprises a number of radio network subsystems (not shown inthe figure) connected to the core network CN. A radio network sub-systemcomprises a radio network controller RNC and one or more B nodes nodeB.The radio network controller RNC is a network node responsible forcontrolling UTRAN radio resources. It corresponds logically to a basestation controller in the GSM system. In each connection between theuser equipment UE and the UTRAN, one RNC is a serving RNC. The main taskof the B node nodeB is to process (channel coding and multiplexing, rateadjustment, decoding, etc.) a layer 1 of an air interface. It alsocarries out some management operations of the basic radio resource, suchas controlling inner circuit power. The B node nodeB correspondslogically to a base station in the GSM system.

The core network CN can be connected to external networks, such IPnetworks IP. In the example of FIG. 1, the core network CN comprises aserving general packet radio service GPRS support node SGSN, a gatewayGPRS support node GGSN and a home subscriber server HSS. Core networksof another type, such as IS-41, may comprise other network nodes.

The support nodes SGSN and GGSN are usually interconnected by a backbonenetwork (not shown in the figure). It is to be noted that the SGSN andGGSN functionalities can also be physically connected to the samenetwork node, in which case the backbone network of the operator isunnecessary. Logically, however, the nodes are different nodes. The IPtelephony is in practice invisible to the elements of the core network.For the support nodes SGSN and GGSN, the IP telephony is only a PDPcontext, i.e. a transmission link, with certain service qualityrequirements. The signaling associated with the IP telephony usuallyterminates at the user equipment and the CSCF, so there is no need forthe SGSN or GGSN to understand it.

The serving GPRS support node SGSN is a node which serves the userequipment UE located in its area. In a packet radio network of thecellular type, each support node SGSN provides mobile data terminals,i.e. the user equipment UE, with packet data service in the area of oneor more cells in its service area. The SGSN can participate incollecting billing information in the access network. The SGSN accordingto the first preferred embodiment of the invention comprises a functionsimilar to the service switching function in an intelligent network.

The GPRS gateway support nodes GGSN connect the operator to systemsexternal to the GPRS network, such as the IP network IP. The GGSN canalso be connected directly to a private company network or a host. TheGGSN operates as a router between an external address and internalrouting data (e.g. SGSN). The GGSN can participate in collecting thebilling information of the access network.

The home subscriber server HSS logically corresponds to the homelocation register in the GSM system, subscriber information for eachsubscriber being stored therein permanently or semi-permanently suchthat the subscriber information is combined with a subscriberidentifier, which, for example, is an IMSI in the GSM system. The CSCFof the IP telephony network has a signaling connection to the HSS.

In the first preferred embodiment of the invention, the access networkcomprises a service control function CSE_A for billing prepaidsubscriptions. This network node responsible for billing can also be anetwork node of a third party, i.e. for instance the provider of aprepaid service. The event to be billed from an account of the prepaidsubscription or from the subscriber of a subscription to be paid inarrears is not necessarily by any means related to the actual bearerservice at all, but the account/subscription can be used for billing allkinds of services, i.e. for various billing events necessary for e.g.e-commerce. In the first preferred embodiment of the invention, it isassumed that the subscriber has a prepaid subscription to the operatorof the access network and the operator of the access network, in turn,has bilateral billing-related contracts with IP telephony operators. Theservice control function CSE_A may comprise all service logic associatedwith prepaid subscription services and control associated with theservice, and necessary databases for the service or a connection to thedatabases. The service control function is only a logical function andit can be internally implemented in different ways. An alternative isthat it is internally decentralized and the related service logic can bedecentralized in different nodes. Also the service information can bedecentralized in different nodes from the service logic. In the firstpreferred embodiment of the invention, however, it is assumed for thesake of clarity that maintenance of the prepaid subscriptions' accountsand the necessary information are located in the same network node.

IP telephony is a general term which covers services from the standardvoice telephony voice over IP VoIP to multimedia applications using IPdata, voice and video in the IP telephony. In addition to the IPtelephony, the above-described system supports other applications, suchas access to the Internet or an intranet. Similarly, an IP call refersto a call which utilizes IP-based user information flow and signaling.The user information may comprise several different components, such asvoice, video image and data. In addition to calls, the IP telephony maycomprise call-like services, which can be unidirectional, directed to agroup (or groups) or broadcast in a given area, for example. In the IPtelephony, mobile communication systems utilize new protocols, such as awireless application protocol WAP.

In addition to prior art means, a system and its network nodesimplementing the functionality of the present invention comprise meansfor implementing functions described in closer detail in connection withFIG. 2, 3 or 4. To be more precise, they comprise either means foridentifying a joint billing subscriber and for transmitting billingtariffs from a network to another and for billing the subscriberaccording to a billing tariff obtained by combining the billing tariffsof the two networks, or means for generating a global billing identifierand for transmitting the identifier to the nodes that collect billinginformation. It is also feasible that the system and its network nodescomprise all means mentioned above. In addition, the user equipment maycomprise means for storing the global billing identifier and fortransmitting the billing identifier to at least one of the networks. Theexisting network nodes and user equipment comprise processors and memorythat can be utilized in the functions of the invention. All changesnecessary for implementing the invention can be carried out asadditional or updated software routines and/or by application circuits(ASIC).

FIG. 2 shows signaling according to the first preferred embodiment ofthe invention when a call using the IP telephony is made from the userequipment UE using a prepaid subscription. It is an example of serviceschargeable from the subscription of the user equipment, for which thefunctionality according to the first preferred embodiment of theinvention can be utilized. In the example of FIG. 2, it is assumed thatthe user equipment has a subscription both to the access operator andthe telephony operator but a prepaid account only to the accessoperator. The subscription to the telephony operator is used by theCSE_T to identify the subscription of the user equipment as a prepaidsubscription. In other embodiments of the invention, the prepaidsubscription can be identified in other ways and in these embodiments,the user equipment only needs a single subscription, preferably asubscription to the access operator. For the sake of clarity, it isassumed that the user equipment has made its presence known to theaccess network by performing a GPRS attach operation. In the GPRS attachprocedure, the SGSN creates a mobility management MM context, and alogical link control LLC is provided between user equipment UE and theSGSN node at the protocol layer.

Furthermore, it is for the sake of clarity assumed that the userequipment UE has activated the PDP context, i.e. packet data address, itwishes to use. The PDP context specifies different data transferparameters, such as a PDP type (X.25 or IP, for example), PDP address(IP address, for example), quality of service QoS and a network serviceaccess point identifier NSAPI. During the activation of the PDP context,the SGSN has encountered a subscriber-specific trigger (detectionpoint), as the result of which it has requested context processinginstructions from at least the service control function of the accessoperator which is responsible for maintaining the account of the prepaidsubscription. The SGSN receives the address of the control functionfrom, for example, the home subscriber server HSS, or it may have beenset as a default value in the trigger. As the processing instructions,the SGSN receives from the control function CSE_A different thresholdvalues, for example, such as a reporting condition by which the CSE_Arequests an announcement from the SGSN when a certain amount ofinformation has been transmitted from the user equipment UE when thebilling is based on the transmitted amount of information. This exchangeof information is not shown in FIG. 2.

Furthermore, it is for the sake of clarity assumed that the userequipment has registered itself in a CSCF and the call is routed to theCSCF. It is irrelevant to the invention how the CSCF is chosen duringregistration. In other embodiments of the invention, the call can berouted to another CSCF in which the user equipment is not registered.

In FIG. 2, the process starts when the user equipment UE transmits aconnection setup request 2-1. The SGSN transmits the message to theGGSN, which transmits the call setup request 2-1 to the CSCF. Receptionof the call setup request 2-1 results in encountering, at the CSCF, atrigger (Detection Point) to initiate the service, which causes the CSCFto transmit a request 2-3 for instructions to the service controlfunction CSE_T of the telephony operator. The service control functionCSE_T detects in step 24 that the call concerns a prepaid subscription,and the service control function CSE_A is responsible for the prepaidaccount of the prepaid subscription. In the first preferred embodimentof the invention, this information is located, for example, in thedatabase of the CSE_T, or the operators may have a common database touse. In another preferred embodiment of the invention, the CSE_T mayinfer, on the basis of the telephone number of the caller, for example,that a prepaid subscription is at issue and request the address of theservice control function CSE_A responsible for the prepaid account fromthe HSS via the CSCF.

Since the subscription is a prepaid subscription, the CSE_T sends, in amessage 2-5, the tariff of the telephony operator and instructs the CSCFthat the tariff of the telephony operator is to be transmitted to theCSE_A and all special events during the call are to be reported to theCSE_A. The message 2-5 preferably comprises the address of the CSE_A.After receiving the address 2-5, the CSCF transmits a message 2-6, whichcomprises the telephony operator tariff information and indicates thetelephony operator to the CSE_A, to the CSE_A maintaining the account ofthe prepaid subscription. If no further intelligent-network-likecontrolling is associated with the service, the connection between theCSCF and the CSE_T is disconnected. After receiving the message 2-6, theCSE_A checks in step 2-7 whether the access operator and the telephonyoperator indicated by the message 2-6 have a billing-related contract.

If the operators have a mutual contract, the CSE_A combines the tariffof the telephony operator and the tariff of the access operator in orderto charge the prepaid account according to the combined tariff. Inaddition, the CSE_A transmits an instruction to the CSCF in a message2-8A to continue call establishment. The message 2-8A may also compriseother information related to the intelligent-network-like controlling,such as arming of detection points. The message 2-8A may also comprise,for example, reporting conditions or changes of previous reportingconditions. When the connection has been established, the prepaidaccount is charged according to the combined tariff mainly on the basisof information reported by the SGSN. If the CSCF detects a specialevent, i.e. an event which could not have been taken into account intariff formation, it informs the CSE_A of the event so the CSE_A canacknowledge the event in the charging of the prepaid account. The accessoperator transmits the telephony operators share in the billing of theconnection to the telephony operator, preferably in arrears.

If the operators do not have a mutual contract, the CSE_A informs theCSCF of this in a message 2-8B, whereafter the CSCF preferablyterminates call establishment and informs the user equipment UE of thefact that the selected telephony operator cannot be used.

In a preferred embodiment of the invention, the tariff of the telephonyoperator is known in the CSCF. In this embodiment, the message 25 doesnot contain the tariff.

In a preferred embodiment of the invention, the CSE_A and the CSE_T maydirectly intercommunicate. In this embodiment, the CSE_T directlyinforms the CSE_A of the tariff of the telephony operator, and the CSE_Areplies to the CSE_T with the message 2-8A or 2-8B. In this embodiment,messages 2-5 and 2-6 are unnecessary but the connection between the CSCFand the CSE_T cannot be disconnected. In this embodiment, the CSE_Ttransmits the information on special events to the CSE_A.

In a preferred embodiment of the invention, the prepaid subscription isa subscription to the telephony operator, in which case the CSE_T (orthe like) is responsible for charging the prepaid subscription. In thisembodiment, the CSE_T detects in step 24 that a connection setup requestsupplied via an access operator A is at issue and requests the accessoperator tariff information from the CSE_A (or a corresponding networknode comprising the tariff information) in the messages 2-5 and 2-6 viathe CSCF. The CSE_A returns the tariff information if the operators havea mutual contract, whereafter the CSE_T combines the tariffs and chargesthe account according to the combined tariff. In another embodiment, thecontract information are located at the CSE_T and it requests the tariffinformation only if a contract exists. Yet in another preferredembodiment of the invention, the CSE_T comprises, besides the contractinformation, also the tariff of the access operator. In this embodiment,tariff information needs not be requested but it will suffice that theCSCF combines the tariff of the access operator with the tariff of thetelephony operator. In this embodiment, when the tariff of the accessoperator changes, the change is updated in the CSE_T. This can beperformed by utilizing automatic updating, for example.

Although in connection with FIG. 2 the first preferred embodiment withits different alternatives has been disclosed in connection with aprepaid subscription, it is obvious to one skilled in the art that theinvention according to the first preferred embodiment can also beapplied in connection with subscribers to be billed in arrears e.g. forproducing a single bill to a subscriber and/or for monitoring a balancelimit.

FIG. 3 shows signaling according to a second preferred embodiment of theinvention. In the example of FIG. 3, it is for the sake of clarityassumed that the user equipment UE has a subscription to the accessoperator, which settles the bills between the operators if the telephonyoperator is not the same as the access operator. Each operator, in turn,settles with its service providers the billing related to the use of theservices. In some other embodiments of the invention, the user may havea subscription both to the access operator and the telephony operator.For the sake of clarity, it is further assumed that the user equipmenthas made its presence known to the access network by carrying out a GPRSattach operation. In the GPRS attach procedure, the SGSN creates amobility management MM context, and a logical link is provided betweenthe user equipment UE and the SGSN node at the logical link control LLCprotocol layer. Furthermore, it is assumed for the sake of clarity thatthe user equipment has been registered in the CSCF, and a call is routedto that CSCF. The way in which the CSCF is chosen in connection with theregistration is irrelevant to the invention. In other preferredembodiments of the invention, a call may be routed to a CSCF in whichthe user equipment is not registered.

In FIG. 3, the process starts when the user equipment activates a PDPcontext, which, according to what has been disclosed above, determinesdifferent data transmission parameters, such as a PDP type (X.25 or IP,for example), PDP address (IP address, for example), quality of serviceQoS and a network service access point identifier NSAPI. Activation ofthe PDP context is started by transmitting a message 3-1 (Activate PDPContext Request) from the user equipment UE to the SGSN. Next, the SGSNand the user equipment may carry out security functions, e.g.authentication of the user equipment. These are not shown in FIG. 3.After receiving the message 3-1, the SGSN retrieves the address of theGGSN and transmits a message 3-2 (Create PDP Context Request) to theGGSN. In response to the message 3-2, in step 3-3 the GGSN generates aglobal billing identifier C_ID. The global billing identifier ispreferably a combination of an integer identifying the PDP context inthe GGSN and the address of the GGSN. The billing identifier thus formedis a globally unique one. Preferably, a running number is used as theidentifying integer. Instead of the address of the GGSN, the address ofanother network element may also be used, the integer then preferablyidentifying the PDP context in the particular network element. Thebilling identifier may also be formed in other ways. The point in thesecond embodiment of the invention is that the billing identifier isunique in the system formed by different interacting networks such thatcall detail records relating to the same PDP context that are suppliedto a billing center always contain the same billing identifier, whichcannot be confused at the billing center with the billing identifiersused by other PDP contexts.

After generating the billing identifier C_ID (and after creating theinformation necessary for routing), the GGSN transmits a message 3-4(Create PDP Context Response), which comprises the billing identifierC_ID as a new parameter. The SGSN separates the billing identifier C_IDfrom the message 34 and, in step 3-5, stores the billing identifier C_IDas the billing identifier to be used in this PDP context, and transmitsthe billing identifier C_ID to the user equipment UE in a message 3-6(Activate PDP Context Accept) indicating that the activation of the PDPcontext has succeeded.

After receiving the message 3-6, in step 3-7 the user equipment UEstores the billing identifier C_ID as the billing identifier related tothe particular PDP context. When the user desires a service from thenetwork, e.g. to set up a call, in step 3-8 the user equipment attachesthe billing identifier to a setup message 3-9 (Set up) and transmits themessage 3-9- to the CSCF. In step 3-10, the CSCF stores the billingidentifier in its memory to be used in the billing of this connection.The CSCF transmits the billing identifier to the MGCF in a message 3-11,and in step 3-12, the MGCF stores the billing identifier in its memoryto be used in the billing of this connection.

FIG. 3 shows no other signaling related to connection setup. After theconnection has been set up, certain network nodes (in the example ofFIG. 3 the SGSN, GGSN, CSCF and MGCF) collect billing information, eachtransmitting call detail records CDR to a billing center BC in messages3-13 a, 3-13 b, 3-13 c, 3-13 d. The call detail records comprise thebilling identifier C_ID. Using the billing identifier C_ID, the billingcenter BC combines the call detail records supplied from the differentnetwork nodes into a sum to be billed from the subscriber. A prepaidaccount can also be charged each time after any of the messages 3-13 a,3-13 b, 3-13 c or 3-13 d has been received, in which case combining thebilling events means that each call detail record comprising the samebilling identifier will charge a certain account. The correct account isfound on the basis of the billing identifier. The billing center can bea separate center or e.g. a network node CSE_T charging the account of aprepaid subscription.

In the second preferred embodiment, the network nodes of the telephonyoperator (CSCF and MGCF) remove the billing identifier C_ID from theirmemory while the connection is being disconnected. In the secondpreferred embodiment, the user equipment UE and the network nodes of theaccess network (SGSN and GGSN) remove the billing identifier C_ID fromtheir memory while the PDP context is being deactivated. Removing refersto the information no longer being available.

In a preferred embodiment utilizing the second embodiment of theinvention, a joint billing subscriber is identified either in the GGSNor the SGSN, and the billing identifier is transmitted to the userequipment only if the subscriber is a joint billing subscriber. In thisembodiment, the user equipment is arranged to attach the billingidentifier to the message 3-9 only if it has received one in the message3-6.

FIG. 4 shows signaling according to a third preferred embodiment of theinvention. The same assumptions are made in the example of FIG. 4 as inthe example of FIG. 3. Furthermore, it is assumed in the example of FIG.4 that the interface between the access layer and the telephony layer islocated between the GGSN and the CSCF.

In FIG. 4, the process starts when the user equipment UE startsactivating the PDP context by transmitting a message 4-1 (Activate PDPContext Request) from the user equipment UE to the SGSN. Next, the SGSNand the user equipment may carry out security functions, e.g.authentication of the user equipment. These are not shown in FIG. 4.After receiving the message 4-1, the SGSN retrieves the address of theGGSN and transmits a message 4-2 (Create PDP Context Request) to theGGSN. In response to the message 4-2, in step 4-3 the GGSN generates aglobal billing identifier C_ID. The global billing identifier isdescribed in closer detail in connection with FIG. 3.

After generating the billing identifier C_ID (and after creating theinformation necessary for routing), the GGSN transmits a message 44(Create PDP Context Response), which comprises the billing identifierC_ID as a new parameter. The SGSN separates the billing identifier C_IDfrom the message 4-4 and, in step 4-5, stores the billing identifierC_ID as the billing identifier to be used in this PDP context. The GGSNalso transmits the billing identifier C_ID to the CSCF a message 4-6. Instep 4-7, the CSCF stores the billing identifier in its memory to beused in the billing of this transmission link. The CSCF transmits thebilling identifier to the MGCF in a message 4-8, and in step 4-9, theMGCF stores the billing identifier in its memory to be used in thebilling of this connection.

When a connection, e.g. a call, has then been set up from the userequipment, certain network nodes (in the example of FIG. 4 the SGSN,GGSN, CSCF and MGCF) collect billing information using the billingidentifier C_ID determined for the transmission link used by theconnection, each network node transmitting call detail records CDR tothe billing center BC. The call detail records comprise the billingidentifier C_ID. The transmission of the call detail records is notshown in FIG. 4. In the third preferred embodiment, the billing centerBC operates in a similar manner to that shown in the second preferredembodiment in connection with FIG. 3; therefore, its operation will notbe described in closer detail herein.

In the third preferred embodiment, the network nodes of the telephonyoperator (CSCF and MGCF) and the network nodes of the access network(SGSN and GGSN) remove the billing identifier C_ID from their memorywhile the PDP context is being deactivated. Removing refers to theinformation no longer being available.

In a preferred embodiment of the invention, the message 4-6 comprisingthe billing identifier C_ID is transmitted to the CSCF only when aconnection is being set up from the user equipment.

In another preferred embodiment of the invention, the CSCF requests thebilling identifier C_ID from the GGSN e.g. in response to receiving asetup message (message 3-9 in FIG. 3). In this embodiment, the GGSN isarranged to transmit the message 4-6 in response to the billingidentifier C_ID request received from the CSCF.

If the interface between the access layer and the telephony layer islocated somewhere else, the billing identifier C_ID is transmitted tothe CSCF via this interface, which means that the message 4-6 shown inFIG. 4 is not needed but some other message/other messages is/aretransmitted instead. If the interface is located e.g. between the HSSand the CSCF, the HSS can transmit the billing identifier to the CSCF.The HSS can be informed of the billing identifier either by the SGSN orthe GGSN.

In preferred embodiments of the invention according to the second andthird preferred embodiments, the global billing identifier is notgenerated in connection with activating the PDP context (transmissionlink) but only when the user of the user equipment desires a servicefrom the network. In these embodiments, messages 3-1 and 3-2 or 4-1 and4-2 are used for requesting generation of a billing identifier eitherdirectly or indirectly, and in the embodiment according to the secondpreferred embodiment, step 3-7 can be omitted since the user equipmentmerely relays the billing identifier generated in the network by theaccess operator to the network node(s) of the telephony operator. Inthese embodiments, the billing identifier is preferably removed from thememory of the network node while the connection is being disconnected.

It is also feasible that the billing identifier is generated in thenetwork node of the telephony operator, from which it is transmittedeither directly or via the user equipment to the network node(s) of theaccess network.

In a preferred embodiment utilizing the second and third embodiments ofthe invention, a joint billing subscriber is identified either in theGGSN or the SGSN, and the billing identifier is transmitted to the userequipment or the CSCF only if the subscriber is a joint billingsubscriber. In such an embodiment utilizing the second embodiment, theuser equipment is arranged to attach the billing identifier to themessage 3-9 only if it has received one in the message 3-6.

The second and third embodiments (and embodiments derived therefrom) ofthe invention may also be used both in connection with subscriptions tobe billed in arrears and balance-limited subscriptions to be billed inarrears and in connection with prepaid subscriptions as well.

Some or all signaling messages shown in FIGS. 3 and 4 may be e.g.messages based on GPRS tunneling protocol GTP, H.323 and/or sessioninitiation protocol SIP protocols.

The signaling messages and steps shown in FIGS. 2, 3 and 4 are not shownin absolute chronological order and they can be implemented in adifferent order from the given one. Other signaling messages can betransmitted and/or other functions can be carried out between themessages and/or steps. For example, in the second preferred embodimentof the invention, it can be checked in step 3-9 whether the operatorshave a contract enabling joint billing, and the process can continue asshown in FIG. 3 when such a contract exists. Some steps shown in FIGS. 2and 3 can also be omitted. If, for example, in the first preferredembodiment of the invention the same operator is both the telephonyoperator and the access operator, the CSE_T and the CSE_A can be thesame service control point, in which case in step 2-4, the CSE_T detectsthat it is itself responsible for the account of the prepaidsubscription, so no message 2-5 will be transmitted but the tariffs arecombined as shown in step 2-7. No message 2-6 will then be transmittedeither. The signaling messages are only examples and they may compriseseveral separate messages for transmitting the same information.Furthermore, the messages may also comprise other information. The namesof the messages may also differ from those disclosed above.

It is to be understood that the above description and the relatedfigures are only intended to illustrate the present invention. Differentvariations and modifications of the invention will be obvious to oneskilled in the art without deviating from the scope and spirit of theinvention disclosed in the attached claims.

1. A method, comprising: receiving in a first network a connectionestablishment request for a connection, the connection being through anetwork node of the first network to a second network such that thenetwork node routes communications to the second network; generating, inresponse to at least the received connection establishment request, aconnection-specific billing identifier for the connection in the firstnetwork in association with activating a packet data protocol context orin association with session initiation protocol messaging; adding thebilling identifier to the received connection establishment request;causing, after adding the billing identifier, the received connectionestablishment request comprising the billing identifier to be forwardedto network nodes of the second network that collect billing informationfor the connection; attaching, in each node that collects billinginformation, the connection-specific billing identifier to the billinginformation collected for the connection; and combining the pieces ofthe billing information collected by different nodes that comprise thesame connection-specific billing identifier, wherein a user terminaldesiring a service uses both the first network and the second network inthe telecommunication system, both networks comprising at least one nodeconfigured to collect billing information.
 2. The method of claim 1,further comprising: causing the connection establishment requestcomprising the connection-specific billing identifier to be forwardedfrom the first network to the second network via an interface betweenthe networks.
 3. The method of claim 1, wherein at least an integer andthe address of one network element is used for forming theconnection-specific billing identifier.
 4. A method comprising: causinga connection establishment request to be sent from a user terminal to afirst network, wherein the connection establishment request requests aconnection, the connection being through a network node of the firstnetwork to a second network such that the network node routescommunications to the second network; receiving a connection-specificbilling identifier in the user terminal, the connection-specific billingidentifier being generated in the first network in association withactivating a packet data protocol context or in association with sessioninitiation protocol messaging; requesting activation of a transmissionlink, wherein requesting activation includes causing theconnection-specific billing identifier to be provided to the secondnetwork; and attaching the connection-specific billing identifier to aservice request supplied from the user terminal to the second network onthe transmission link to establish the connection to the second network.5. The method of claim 4, further comprising: causing theconnection-specific billing identifier to be maintained in the userterminal as long as the transmission link is active.
 6. A system,comprising: a first network and a second network configured to provide asubscriber with a service, each of the first network and the secondnetwork comprising at least one node to collect billing information,wherein the system is configured to: generate a connection-specificbilling identifier for a connection in association with activating apacket data protocol context or in association with session initiationprotocol messaging, wherein the connection-specific billing identifieris generated in the first network and in response to at least aconnection establishment request received from a user terminal for aconnection, wherein the connection is through a network node of thefirst network to the second network such that the network node routescommunications to the second network, add the billing identifier to thereceived connection establishment request, cause the connection-specificbilling identifier to be transmitted by causing forwarding of thereceived connection establishment request comprising the billingidentifier to one of the at least one node of the second network thatcollects billing information, and combine the pieces of billinginformation for the connection that comprise the sameconnection-specific billing identifier; wherein the at least one node ofthe first network and second network that collects billing informationare configured to attach the connection-specific billing identifier tothe billing information for the connection.
 7. The system of claim 6,wherein the connection-specific billing identifier is generated in oneof the at least one node of the first network that collects billinginformation.
 8. The system of claim 6, further configured to transmitthe connection-specific billing identifier from the first network to thesecond network via an interface between the first and the secondnetworks.
 9. The system of claim 6, further configured to generate theconnection-specific billing identifier in such a way that the generatedconnection-specific billing identifier comprises the address of anetwork node in the first network and an integer.
 10. A system,comprising: a first network and a second network configured to provide asubscriber with a service, each of the first network and the secondnetwork comprising at least one node to collect billing information;wherein the first network is an access network, and in order to use theaccess network the subscriber must activate a packet data address;wherein the system is configured to: generate a connection-specificbilling identifier in association with activating a packet data protocolcontext or in association with session initiation protocol messaging, aconnection associated with the connection-specific billing identifierbeing established through a network node of the first network to asecond network such that the network node routes communications to thesecond network, cause, during the connection establishment, the billingidentifier to be transmitted to the second network and the at least onenode of the second network that collects billing information, andcombine pieces of billing information for the connection that comprisethe same connection-specific billing identifier; and wherein the atleast one node of the first network and the second network to collectbilling information are configured to attach the connection-specificbilling identifier to the billing information for the connection. 11.The system of claim 10, further configured to cause theconnection-specific billing identifier to be transmitted from the firstnetwork to the second network via user equipment.
 12. An apparatuscomprising at least one processor and at least one memory includingcomputer program code, the at least one memory and the computer programcode configured to, with the at least one processor, cause the apparatusat least to: receive a connection-specific billing identifier for aconnection from a first network in response to at least a connectionestablishment request to establish the connection, theconnection-specific billing identifier being received in associationwith activating a packet data protocol context or in association withsession initiation protocol messaging the connection being through anetwork node of the first network to a second network such that thenetwork node routes communications to the second network; and directtransmission of the connection establishment request with theconnection-specific billing identifier to the second network in arequest for obtaining a service over the connection to be established inresponse to at least the connection establishment request, wherein theapparatus is caused to function in a telecommunication system whichcomprises the first network and the second network to provide asubscriber with the service, each of the first network and secondnetwork comprising at least one node to collect billing information forthe connection.
 13. The apparatus of claim 12, wherein the apparatuscaused to receive the connection-specific billing identifier includesbeing caused to receive the connection-specific billing identifier inconnection with activation of a packet data address between the userequipment and the first network.
 14. The apparatus of claim 12, whereinthe at least one memory is configured to store the connection-specificbilling identifier.
 15. An apparatus, comprising: generating means forgenerating, in response to at least receiving a connection establishmentrequest for a connection, a connection-specific billing identifier to beused for combining billing information for the connection, theconnection-specific billing identifier being generated in associationwith activating a packet data protocol context or in association withsession initiation protocol messaging, the connection being through anetwork node of a first network to a second network such that thenetwork node routes communications to the second network; and includingmeans for including the connection-specific billing identifier into thereceived connection establishment request before forwarding the receivedconnection establishment request to facilitate billing for theconnection using the connection-specific billing identifier in the firstnetwork and the second network.
 16. An apparatus, comprising: collectingmeans for facilitating the collecting of billing information for aconnection, the connection being through a network node of a firstnetwork to a second network such that the network node routescommunications to the second network; receiving means for receiving, inthe second network, a connection establishment request comprising aconnection-specific billing identifier for the connection in associationwith activating a packet data protocol context or in association withsession initiation protocol messaging; and storing means for causingstoring of the connection-specific billing identifier to be used inbilling for the connection.
 17. An apparatus comprising at least oneprocessor and at least one memory including computer program code, theat least one memory and the computer program code configured to, withthe at least one processor, cause the apparatus at least to: generate,in response to at least a connection establishment request for aconnection, a connection-specific billing identifier for the connectionin association with activating a packet data protocol context or inassociation with session initiation protocol messaging, theconnection-specific billing identifier to be used to combine billinginformation relating to the connection in a multi-network communicationsystem, the connection being through a network node of a first networkto a second network such that the network node routes communications tothe second network, and include the connection-specific billingidentifier into the connection establishment request before causingforwarding of the connection establishment request for the connectionthat caused the billing identifier to be generated to facilitate billingfor the connection using the connection-specific billing identifier inthe first network and the second network.
 18. The apparatus of claim 17,wherein the apparatus is further caused to: collect billing informationfor the connection for the first network; and cause the billinginformation for the connection for the first network to be provided to abilling center for combination with billing information for theconnection for the second network.
 19. A method, comprising: receiving aconnection establishment request for a connection, the connection beingthrough a network node of a first network to a second network such thatthe network node routes communications to the second network;generating, in response to at least the received connectionestablishment request, a connection-specific billing identifier for theconnection to be used for combining billing information for theconnection in association with activating a packet data protocol contextor in association with session initiation protocol messaging; includingthe billing identifier into the received connection establishmentrequest; and causing, after including the billing identifier in thereceived connection establishment request, the received connectionestablishment request to be forwarded to facilitate billing for theconnection using the connection-specific billing identifier in the firstnetwork and the second network.
 20. The method of claim 19 furthercomprising: collecting billing information for the connection for thefirst network; and causing the billing information for the connectionfor the first network to be provided to a billing center for combinationwith billing information for the connection for the second network. 21.An apparatus comprising at least one processor and at least one memoryincluding computer program code, the at least one memory and thecomputer program code configured to, with the at least one processor,direct the apparatus at least to: receive a message comprising aconnection-specific billing identifier for a connection, theconnection-specific billing identifier being generated in associationwith activating a packet data protocol context or in association withsession initiation protocol messaging, the connection being through afirst network to a second network such that communications are routedfrom the first network to the second network, and wherein the messagefurther comprises a piece of billing information for the connection froma network node; and combine the piece of billing information withanother received piece of billing information using theconnection-specific billing identifier.
 22. A method comprising:receiving a message comprising a connection-specific billing identifierfor a connection, the connection-specific billing identifier beinggenerated in association with activating a packet data protocol contextor in association with session initiation protocol messaging, theconnection being through a first network to a second network such thatcommunications are routed from the first network to the second network,and wherein the message further comprises a piece of billing informationfor the connection from a network node; and combining the piece ofbilling information with another received piece of billing informationusing the connection-specific billing identifier.
 23. A methodcomprising: causing billing information to be collected for aconnection, the connection being through a network node of a firstnetwork to a second network such that the network node routescommunications to the second network; receiving, in the second network,a connection establishment request comprising a connection-specificbilling identifier for the connection in association with activating apacket data protocol context or in association with session initiationprotocol messaging; and causing the connection-specific billingidentifier to be used in billing for the connection to be stored.
 24. Anapparatus comprising at least one processor and at least one memoryincluding computer program code, the at least one memory and thecomputer program code configured to, with the at least one processor,cause the apparatus at least to: cause billing information to becollected for a connection, the connection being through a network nodeof a first network to a second network such that the network node routescommunications to the second network; receive, in the second network, aconnection establishment request comprising a connection-specificbilling identifier for the connection in association with activating apacket data protocol context or in association with session initiationprotocol messaging; and cause the connection-specific billing identifierto be used in billing for the connection to be stored.